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Posted by Heatpro on December 02, 2005 at 21:12:49:
In Reply to: to Heat Pro Re: Burnham PIN6 posted by peter on December 01, 2005 at 21:10:36:
It's an old American Standard A-3 boiler converted to gas in the 70's. The ratings stamped on the unit are Gross output 173 MBH and sq. feet of steam is 541. Is the unit we discussed close enough to these specs or do you still think it's too big?
You don't want to go by those specs. The unit was converted to gas from solid fuel like wood and coal. The old boiler was about 50% efficient with solid fuel and dropped to about 35% efficiency when converted. You've been heating the house with a boiler that couldn't deliver for 541 sq ft of steam. - probably about 400 sq ft = 96,000 btuh.
Now that is pretty close to what your new boiler is rated at 108 mbh. However, you do not state what the radiation is. No matter which boiler you get, it will have to satisfy the radiation or it will run and run without end if it is too small, or it will cycle fast if too big, so you are going to have to account for the total sq ft of steam radiation you have and then you can add more boiler output in an additional 1/3rd to satisfy the pipe and boiler heatup.
http://www.hydronicnetwork.net/hydronic/rad/edr.htm
Picking the boiler based on old boilers converted to gas is no help to you; just another raw guess.